1. Field of the Invention
The invention relates to packing which is used in a crimp assembly. Also, the invention relates to a production method of a crimp assembly using the packing, a production method of a battery housing lid using the packing, and a production method of a battery using the packing.
2. Description of the Related Art
When producing a crimp assembly by fitting a crimp member to an object by a crimping process, packing may be provided in a space between the object and the crimp member in order to make the space air-tight or fluid-tight. Examples of such a crimp assembly include a sealed secondary battery such as a lithium ion secondary battery or a nickel-hydrogen battery, and a battery housing lid thereof. The sealed secondary battery is installed in an electric vehicle and a hybrid vehicle. Also, the sealed secondary battery is used more and more widely as a power source and an auxiliary power source of the electric vehicle and the hybrid vehicle. Accordingly, there is an increasing demand for improving performance of the sealed secondary battery, for example, an increasing demand for high output capacity in the market. Also, there is an increasing demand for improving reliability of the sealed secondary battery, such as an increasing demand for preventing fluid leak even under a severe condition.
For example, a sealed battery disclosed in Japanese Patent Application Publication No. JP (A) 8-77999 includes a battery housing main body which has a bottomed hollow rectangular column shape, and which has an opening portion on one side; and a battery housing lid which closes the opening portion of the battery housing main body, and which has an insertion hole. Further, this battery includes plural electrode plates which generate electromotive force; a current collecting washer which is connected to each of the electrode plates; and a terminal member which is connected to the electrode plates. Among them, the terminal member includes a main body portion having a rectangular column shape; and a cylinder portion having a hollow cylindrical shape. Also, the main body portion of the terminal member is arranged outside the battery housing lid. One end of the cylinder portion of the terminal member is fixed to the main body portion. The other end of the cylinder portion of the terminal member is inserted in the insertion hole of the battery housing lid. Packing is provided between the terminal member and the battery housing lid. The packing is obtained by forming a resin member. The packing is formed so as to cover a surface of the main body portion facing the battery housing lid, and a surface of the cylinder portion facing an inner peripheral surface of the insertion hole. The packing functions as a seal member that provides air-tight sealing between the terminal member and the battery housing. In addition, the packing function as an insulation member between the battery housing lid and the terminal member. In the cylinder portion of the terminal member, an end portion which protrudes beyond the packing and the current collecting plate inside the battery housing lid is subjected to a crimping process.
However, in the aforementioned sealed battery, since the terminal member is solid except the lower end portion, the weight of the terminal member is heavy. Also, in the battery, the packing is simply compressed between the inside of the battery housing lid and the portion of the terminal member subjected to the crimping process, whereby electrolytic solution is sealed. In this configuration, there are variations in the sealing performance. As a result, it is difficult to reliably maintain high air-tightness and fluid-tightness for a long period.
Accordingly, inventors propose various structures of a sealed battery and various production methods thereof. One of the proposed sealed battery includes a metallic battery housing lid which constitutes a connection terminal with one pole; and a terminal member which is fitted to the battery housing lid in an insulating state, and which constitutes a connection terminal with the other pole. In the sealed battery, packing with an electric-insulating property is provided between the hollow cylindrical terminal member which is closed at one end, and a penetration hole for the terminal member, which is provided in the battery housing lid. Further, in the sealed battery, the packing is compressed by a compression deformation portion which bulges in a radial direction at one end of the terminal member so that sealing performance is obtained and the terminal member is fixed.
In this configuration, the hollow cylindrical terminal member which is closed at one end is used. Also, the sealing performance of the packing is obtained, and the terminal member is fixed by the compression deformation portion formed by deforming the portion at the end of the terminal member. Accordingly, since only the hollow cylindrical terminal member whose weight is light is used, weight and cost can be reduced. Further, high sealing performance can be reliably obtained.
Also, in a production method of the proposed sealed battery, first, the hollow cylindrical terminal member which is closed at one end is inserted in the penetration hole provided in the battery housing lid from the side of the one end, through the packing including the cylinder portion which has a cylindrical shape, and which has an electric insulating property and a plastic property, and a flange portion which is positioned at one end of the cylinder portion, and which expands outward in the radial direction. Next, in the terminal member, a portion at the one end which protrudes beyond the battery housing lid is caused to bulge outward in the radial direction by a bulging process. Subsequently, the portion of the terminal member is compressed in an axial direction to be deformed, whereby the sealing performance of the packing is obtained, and the terminal member is fixed. Further, an electrode plate group is housed in a battery housing main body, and the battery housing lid is joined to the battery housing main body. Finally, one end wall of the terminal member is joined to an end surface of the electrode plate group which has one polarity, and an end surface of the electrode plate group which has the other polarity is joined to a bottom wall of the battery housing main body, whereby the sealed battery is produced.
In this sealed battery, when the terminal member is fixed, the portion at one end of the terminal member is caused to bulge in the radial direction, and then is compressed in the axial direction so as to be deformed. Also, at this time, in the cylinder portion of the packing between the terminal member and the penetration hole of the battery housing lid, a diameter of a portion protruding beyond the battery housing lid is increased in the radial direction. In this case, strong tensile stress in the circumferential direction is applied to the portion whose diameter is increased, in the cylinder portion of the packing. Therefore, the portion to which the stress is applied may be torn or cracked. If such damage occurs in the packing, leakage of gas or fluid may occur at the damaged portion, and thus reliability of air tightness and fluid tightness may be decreased.